>>>>> Hervé Pagès <hpa...@fredhutch.org>
>>>>> on Tue, 29 Mar 2016 12:19:12 -0700 writes:
> Hi,
> On 03/07/2016 09:26 AM, Martin Maechler wrote:
>> I'm proposing to signal an error (from R >= 3.3.0) in such
>> examples -- which do "work" in R 3.2.x and earlier :
>>
>>> f <- NULL; body(f) <- quote(sin(a+1)); f
>> function ()
>> sin(a + 1)
>> <environment: 0x48f9798>
>>
> This works because formals() (the getter) works on things that are
> not a function.
>>> g <- NULL; formals(g) <- alist(x = pi, y=); g
>> function (x = pi, y)
>> NULL
>> <environment: 0x4e6dfe8>
>>>
> And this works because body() (the getter) also works on things that
> are not a function.
of course (twice).
>> The proposal is that the underlying C code will signal an error
>> when such replacement functions would create a function out of
>> "something not a function".
> Why modify the C code for this?
My current proposal would change both the C code *and* the following.
> This is how formals() and body() are defined at the moment:
>> formals
> function (fun = sys.function(sys.parent()))
> {
> if (is.character(fun))
> fun <- get(fun, mode = "function", envir = parent.frame())
> .Internal(formals(fun))
> }
> <bytecode: 0x153cde0>
> <environment: namespace:base>
>> body
> function (fun = sys.function(sys.parent()))
> {
> if (is.character(fun))
> fun <- get(fun, mode = "function", envir = parent.frame())
> .Internal(body(fun))
> }
> <bytecode: 0xb452e8>
> <environment: namespace:base>
> Not sure why they are not simply doing fun <- match.fun(fun) but if
> they were, then they would signal an error when called on something
> that is not a function.
Using match.fun() will probably be "the right thing" in the
future.
However, as this has been an unchanged part of R for very many years,
my current proposal would only signal *warnings* for now.
Thank you, Herve, for the reminder about this. Indeed, I *have*
been wanting to commit my proposal to R-devel for a long time
and somehow have always been anxious to produce too many
negative effects with CRAN / Bioconductor packages producing
warning (or errors) after the change and me not having the time
to send e-mails to all the package maintainers.
As I won't have time for that anyway, and as "good package
maintainers" should at least browse, if not read the R-devel
mailing list (;-),
your prompting now makes me commit my proposal (to R-devel only;
*not* R 3.4.0 alpha) and leave the resulting "problems" to the
package maintainers affected.
Martin
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